Generally, nanodiamonds, which are very small diamond particles having a size of several nm, are prepared by exploding a mixture of TNT and hexogen in an inert medium, such as CO2, an inert gas or water, to synthesize a diamond aggregate (an explosion process), which is then milled by using a bead mill.
Since such nanodiamonds have a high refractive index and are highly transparent, they are expected to be useful as optical material, and are also being considered for application as a polishing agent thanks to the high hardness thereof. In addition, nanodiamonds may be applied to various industrial fields thanks to their nanoparticle properties.
However, since the surfaces of nanodiamond particles are hydrophilic, the nanodiamonds cannot be dispersed in hydrocarbon solvents (heptane, decane, etc.) and almost all organic solvents, and also an epoxy resin. Further, nano-materials, such as nano-carbon, including the nanodiamonds, may easily aggregate, so that it is difficult to realize their special properties as nano-materials. For example, the nanodiamonds are expected to be industrially used as a polishing agent thanks to the high hardness thereof, and as an optical material for the high transparency or high refractive index thereof, but the applicability thereof is limited by the above-mentioned problems.